EP3733733A1

EP3733733A1 - Polyesters from lignin-based monomers

Info

Publication number: EP3733733A1
Application number: EP19172061.4A
Authority: EP
Inventors: Richard Vendamme; Pablo ORTIZ URRACA
Original assignee: Vito NV
Current assignee: Vito NV
Priority date: 2019-04-30
Filing date: 2019-04-30
Publication date: 2020-11-04
Also published as: EP3962985C0; WO2020221730A1; US20220213264A1; EP3962985A1; CN114040935A; EP3962985B1; CN114040935B

Abstract

The invention is directed to polyesters comprising the following repeating unit of formula I:

wherein:
R¹ and R² independently represent H or CH₃,
R³ and R⁴ independently represent H or OCH₃,
R⁵ independently represents C_1-16alkyl-O(C=O)R⁷(C=O); C_1-16alkyl(C=O); (C=O)C_2-3alkyl(C=O); C_1-16alkyl(C=O)OR⁷O(C=O)C_1-16alkyl;
C_1-16alkyl(C=O)OR⁷ or (C=O)C_2-3alkyl(C=O)OR⁷O(C=O)C_2-3alkyl,
R⁷ independently represents C_1-20alkyl; benzene or furan,
R⁶ represents CH₂ or (C=O),
n = 0-3,
m ≥ 10.

The invention is also directed to a process for the preparation of these polyesters, wherein the monomer or monomer mixture is heated in the presence of a catalyst to a temperature of 100-300 °C under a pressure below 10 kPa .

Description

TECHNICAL FIELD

The present invention is directed to polyesters. These polyesters can replace polyethylene terephthalate(PET) in many applications.

BACKGROUND ART

Polyethylene Terephthalate (PET) is one of the most widely produced polymers in the world. It is naturally transparent and is extensively used in daily life. Its main uses are as synthetic fibers (termed "polyester") and for bottling and packaging, due to its excellent moisture barrier. PET has interesting properties such as being strong but at the same time lightweight and flexible. Moreover, it is safe, non-toxic and can be easily recycled. Polyethylene terephthalate, as its name indicates, is synthesized by the condensation between terephthalic acid and ethylene glycol, both derived from fossil resources.
2,5-furandicarboxylic acid (FDCA) is a bio-based alternative to terephthalic acid that has gained increased attention in the last years. FDCA can be derived from sugars and it has shown the ability to replace terephthalic acid in a variety of applications. Among them, the most remarkable example is the production of polyethylene furanoate (PEF), which gives the resulting polymer better barrier, thermal and mechanical properties when compared to PET. Moreover, the polymer can be fully bio-based. However, the synthesis of aromatic structures from sugars is not the most straightforward pathway, especially considering that aromatic structures can already be found in nature.

SUMMARY OF THE INVENTION

There is a need to find a different bio-based substitute for terephthalic acid to be able to replace the fossil-derived aromatics in PET.
One object of the invention is to provide bio-based polyesters, which polyesters are easy to produce and can be recycled.
The present invention is directed to a polyester comprising the repeating unit according to formula I:
wherein:

R¹ and R² independently represent H or CH₃,
R³ and R⁴ independently represent H or OCH₃,
R⁵ independently represents C_1-16alkyl-O(C=O)R⁷(C=O); C_1-16alkyl(C=O);
(C=O)C_2-3alkyl(C=O); C_1-16alkyl(C=O)OR⁷O(C=O)C_1-16alkyl;
C_1-16alkyl(C=O)OR⁷ or (C=O)C_2-3alkyl(C=O)OR⁷O(C=O)C_2-3alkyl,
R⁷ independently represents C_1-20alkyl; benzene or furan,
R⁶ represents CH₂ or (C=O),
n = 0-3,
m ≥ 10.

The polyesters according to the invention have the advantage that they can be prepared from fully bio-based monomers. Further, the polyesters according to the invention can be used for the same products as existing polyesters, for example PET, which are made from fossil-derived aromatics.
The polyesters according to the invention can be prepared from lignin-based monomers. Lignin is a by-product of cellulose production. As a consequence of the harsh reaction conditions used to separate lignin from polysaccharides, lignin degradation and condensation takes place. Most of the depolymerization protocols for cellulose make use of high temperatures and harsh reaction conditions (acidic or basic) which result in low yield of diverse monomers. Nevertheless, mild fractionation and/or depolymerization conditions of lignin and strategies to stabilize the intermediates formed during depolymerization (either by using reductive catalysts or additives) allow the isolation of monomers from lignin in good yields and selectivity (Chem. Rev. 2018 118, 614; Chem. Soc. Rev. 2018, 47, 852).
There are a few examples of polymers based on monomers that are derived from lignin. WO2011143379A2 describes the transformation of vanillin into acetyldihydroferulic acid and its polymerization to poly (dihydroferulic acid). Further, WO2014075057A8 describes a thermoplastic copolymer comprising poly(dihydroferulic acid-co-ferulic acid) and WO2017123587A1 describes the synthesis of polymers from (hydroxy)(alkyl)(dihydro)ferulic acid and/or (hydroxy)(alkyl)(dihydro)cumaric acid. A disadvantage of these polymers is however that the polymers are based on only a few monomers and the properties of the resulting polymers cannot be tuned. The polymers can therefore not replace PET in all applications.,
The polyesters according to the invention can be prepared from lignin-based monomers. The lignin-based monomers can be prepared by modification of lignin-based precursors. The lignin-based precursors are 4-hydroxyalkylphenols according to formula A:

R¹ and R² independently represent H or CH₃
R³ and R⁴ independently represent H or OCH₃
R = CH₃ or OH
n = 0-4

Both lignin-based molecules and model compounds, petroleum-derived compounds whose structure reproduces the lignin-based molecules, can be used as precursors according to the invention. Both, lignin-based molecules and model compounds, are thus referred to as lignin-based precursors.
The lignin-based monomers can be obtained by modification of the phenolic hydroxyl group and/or the modification of the aliphatic hydroxyl group of a lignin-based precursor according to formula A.

Polyesters

The polyesters according to the invention comprise the repeating unit according to formula I:
wherein:

According to one preferred embodiment of the invention the polyesters comprise a repeating unit of formula II:

R¹ and R² independently represent H or CH₃
R³ and R⁴ independently represent H or OCH₃
R⁵ represents C_1-16alkyl(C=O) or (C=O)C_2-3alkyl(C=O)
n = 0-3
m = >10

According to a second preferred embodiment of the invention the polyesters comprise a repeating unit of formula III:

R¹ and R² independently represent H or CH₃
R³ and R⁴ independently represent H or OCH₃
R⁵ independently represents C_1-16alkyl-O(C=O)R⁷(C=O)
R⁷ independently represents C_1-20alkyl; benzene or furan
n = 0-3
m = >10

According to a third preferred embodiment of the invention the polyesters comprise a repeating unit of formula IV:

R¹ and R² independently represent H or CH₃
R³ and R⁴ independently represent H or OCH₃
R⁵ independently represents C_1-16alkyl(C=O)OR⁷O(C=O)C_1-16alkyl or C_1-16alkyl(C=O)OR⁷or (C=O)C_2-3alkyl(C=O)OR⁷O(C=O)C_2-3alkyl
R⁷ independently represents C_1-20alkyl; benzene or furan
R⁶ represents CH₂ or (C=O)
n = 0-3
m = >10

Process

The polyesters according to formulas I-IV can be prepared by heating a monomer or monomer mixture in the presence of a catalyst to a temperature of 100-300 °C under a pressure below 10 kPa.
The temperature during the reaction is preferably 120-280 °C, more preferably 130-260 °C and most preferably 150-240 °C. The temperature may vary during the reaction time. It is for example, possible to start the reaction at a lower temperature and raise the temperature afterwards.
At least a part of the reaction is usually carried out under a pressure below 10 kPa. This is a vacuum pressure, which is used during the reaction for the removal of water (in case of esterification reaction) or alcohol (in case of transesterification reaction). The pressure is preferably below 8 kPa, more preferably below 5 kPa, most preferably below 2 kPa.
The reaction time is typically between 1-50 hours, preferably between 5 and 40 hours, more preferably between 10 and 30 hours.
The catalyst can be any esterification catalyst. The catalyst preferably is chosen from a metal oxide such as Sb₂O₃, GeO₂, TiO₂, PbO or MgO; a metal alkoxide such as Ti(OC₄H₉)₄, Ti[OCH(CH₃)2]₄ or Zr(OC₄H₉)₄; a metal acetate such as Mg(OCOCH₃)₂, Mn(OCOCH₃)₂, Zn(OCOCH₃)₂, Sb(OCOCH₃)₃ or Sn[OCO(C₂H₅)CH(CH₂)CH₃]₂; a (Lewis) acid such as H₂SO₄, polyphosphoric acid or SnCI; or any combinations thereof.
The catalyst is used in a low amount, preferably in an amount between 0.001 and 5 mol%, more preferably between 0.005 and 4 mol%, most preferably between 0.01 and 3 mol%.
The catalyst can be added in a single charge or it can be added in more than one charges. Adding the catalyst in more than one charges, specially using two different catalysts, is suited when the polymerization is carried out in two steps. For example, a first step in which oligomers are formed, and a second step for the polycondensation. Polyester formation might also be carried out in one step.
The copolymers are prepared by condensation of lignin-based monomers and other comonomers. The molar fraction of lignin-based monomers to other comonomers is typically between 0.1-0.9, but preferably between 0.3-0.7, more preferably between 0.4-0.6 and most preferably between 0.45-0.55.

Monomers

The lignin-based precursors are 4-hydroxyalkylphenols according to formula A:

The lignin-based monomers can be obtained by modification of the phenolic hydroxyl group and/or the modification of the aliphatic hydroxyl group of a lignin-based precursor according to formula A.
Reactions to functionalize the precursor can target either one or both hydroxyl groups of the lignin-based monomers. Because of the different reactivity of the phenolic and aliphatic hydroxyls, selective functionalization of phenolic hydroxyl is possible.
According to an embodiment lignin-based monomers can be prepared that have a structure according to formula V:

R¹ and R² independently represent H or CH₃
R³ and R⁴ independently represent H or OCH₃
R⁵ represents C_1-16alkyl or (C=O)C_2-3alkyl
R⁸ represents H or C_1-4alkyl
n = 0-3

The lignin-based monomers according to formula V can be synthesized by modification of phenolic hydroxyl group of lignin-based precursors in formula A, so that a terminal carboxylic acid or ester group is incorporated. Such functionalization might be carried out by reaction with different chemicals, such as but not limited to molecules containing a halogen and a carboxylic acid, such as chloroacetic acid, bromoacetic acid, 3-chloropropionic acid, 3-bromopropionic acid, 4-chlorobutyric acid and the like; molecules containing a halogen and a terminal ester, such as methyl 3-chloropropionate, methyl 4-chlorobutyrate and the like; cyclic anhydrides such as succinic anhydride or glutaric anhydride; cyclic lactones such as γ-butyrolactone or δ-valerolactone.
The selective functionalization of phenolic hydroxyl group can be achieved in different ways. One option is by using a base that will deprotonate the phenolic hydroxyl but not the aliphatic hydroxyl. Examples of common bases that meet this criteria include, but are not limited to: ammonia, metal hydroxides M(OH)_x, preferably alkali metal hydroxides, such as NaOH or KOH, and carbonate salts with the formula M_x(CO3)_y, such as Na₂CO₃ or K₂CO₃.
In the case that the functionalization results in the incorporation of a carboxylic acid group, it can later be converted into its ester by a transesterification reaction with an alcohol of up to four carbon atoms, but preferably methanol is used.
According to another embodiment lignin-based monomers can be prepared that have a structure according to formula VI:

R¹ and R² independently represent H or CH₃
R³ and R⁴ independently represent H or OCH₃
R⁵ independently represents C_1-16alkyl
n = 0-3

Monomers described in formula VI can be synthesized by modification of the phenolic hydroxyl group of lignin-based precursors in formula A. The phenolic hydroxyl can be reacted to attach a terminal aliphatic hydroxyl group. This reaction can be performed with different chemicals, such as but not limited to cyclic ethers, such as tetrahydrofuran; cyclic carbonates such as ethylene carbonate or propylene carbonate; and haloalcohols, such as 2-chloroethanol, 2-iodoethanol, 3-chloro-1-propanol, 3-bromo-1-propanol and 4-chlorobutanol. The functionalization of the hydroxyl group will lead to the unitslisted in formula VI where R⁵ is an alkyl chain with 1-16 carbon atoms. The selective functionalization of phenolic hydroxyl group can be achieved in different ways. One option is by using a base that will deprotonate the phenolic hydroxyl, but not the aliphatic hydroxyl. Examples of common bases that meet this criteria include, but are not limited to: ammonia, metal hydroxides M(OH)_x, preferably alkali metal hydroxides (such NaOH or KOH) and carbonate salts with the formula M_x(CO3)_y (such as Na₂CO₃ or K₂CO₃).
According to a further embodiment lignin-based monomers can be prepared that have a structure according to formula VII:

R¹ and R² independently represent H or CH₃
R³ and R⁴ independently represent H or OCH₃
R⁵ independently represents C_1-16alkyl or (C=O)C_2-3alkyl
R⁶ represents H or C_1-4alkyl
n = 0-3

Monomers described in formula VII can be synthesized by modification of both the aliphatic and the phenolic hydroxyl group of lignin-based precursors in formulaA. Both the aliphatic and the phenolic hydroxyl can be modified to incorporate a terminal carboxylic acid or an ester. The functionalization of both hydroxyl groups may be carried out in one step or in two steps. In the second case, first the monomers described in formula V are prepared and the aliphatic hydroxyl is then modified. The chemical modification can be achieved with different chemicals, such as but not limited to: molecules containing a halogen and a carboxylic acid, such as chloroacetic acid, bromoacetic acid, 3-chloropropionic acid, 3-bromopropionic acid, 4-chlorobutyric acid and the like; molecules containing a halogen and a terminal ester, such as methyl 3-chloropropionate, methyl 4-chlorobutyrate and the like; cyclic anhydrides such as succinic anhydride and glutaric anhydride; cyclic lactones such as γ-butyrolactone or δ-valerolactone. The functionalization of both the aliphatic and the phenolic hydroxyl group can be achieved using a base with a higher pKa than both aliphatic and aromatic OH. Examples of such bases include but are not limited to metal hydrides such sodium hydride; metal alkoxides such as sodium ethoxide; metal amides such as sodium amide, lithium diisopropylamide, lithium diethylamide; organolithium compounds such as butyl lithium.
According to a further embodiment lignin-based monomers can be prepared that have a structure according to formula VIII:

R¹ and R² independently represent H or CH₃
R³ and R⁴ independently represent H or OCH₃
R⁵ independently represents C_1-16alkyl or (C=O)C_2-3alkyl
R⁶ independently represents H or C_1-4alkyl
n = 0-3

Monomers described in formula VIII can be synthesized by modification of both the aliphatic and the phenolic hydroxyl group of lignin-based precursors in formula A. Two reactions are required. First, the phenolic hydroxyl is modified with the chemistry described in previous embodiments to anchor an aliphatic hydroxyl or a carboxylic acid group. Then an oxidation reaction is performed, which converts the aliphatic hydroxyl group(s) into carboxylic acids. If a carboxylic acid group is attached to the phenolic hydroxyl, the aliphatic hydroxyl will be oxidized to the carboxylic acid. If an aliphatic hydroxyl was attached to the phenolic hydroxyl, both aliphatic hydroxyls will be oxidized to carboxylic acids. The oxidation can be carried out in two steps, namely, first from the alcohol to the aldehyde and subsequently to the acid or in one step, from the alcohol to the acid. The latter is preferred. Several reagents can be used, such as but not limited to chromium oxides (Jones reagent, CrO₃/H₅IO₆); ruthenium oxides or chlorides (RUCl₃/H₅IO₆, RuCl₃/K₂S₂O₈, RuO₄); Cu(MnO₄)₂ oxidation; TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxy)-catalysed oxidation with sodium hypochlorite or with trichloroisocianuric acid; and methods using peroxides. The resulting dicarboxylic acids can be converted to the corresponding esters by transesterification reaction.

Polymers

The polymers according to formula I can be prepared by the polymerization process as described above.
Mixtures of monomers can be utilized in the polymerization process, some of the substituents (R¹, R², R³ and R⁴) might be different in the repeating units. Therefore, the term independently in the formula, indicates that within the repeating units in the polymer the substituents (R¹, R², R³ and R⁴) can be elected independently of one another. Mixtures of dicarboxylic acids, mixtures of diesters and mixtures of diols can be used, and therefore the term independently for R⁷, C_1-20alkyl, C_1-16alkyl and C_2-3alkyl represents an alkyl chain with the listed number of carbon atoms with their corresponding hydrogen atoms. In the following embodiments, a more detailed description of the polymers and the way of synthesizing them will be provided.
The homopolymers are the result of a polymerization reaction of lignin-based monomers with one aliphatic hydroxyl and one carboxylic acid functionality. In one embodiment, homopolymers with the following repeating formula (Formula II) are described. Within the context of the present invention, the repeating units of the homopolymers in Formula II are not necessarily the same based on different (R¹, R², R³, R⁴ and R⁵) substituents in the repeating units. In a preferred embodiment the repeating units of the homopolymers in Formula II are the same.

R¹ and R² independently represent H or CH₃
R³ and R⁴ independently represent H or OCH₃
R⁵ represents C_1-16alkyl or (C=O)C_2-3alkyl
n = 0-3
m = >10

Formula II

The homopolymers in formula II are prepared from monomers described in Formula V according to the above-mentioned polymerization process.
Besides homopolymers, the present invention also provides copolymers comprising either lignin-based monomers functionalized to form diols or lignin-based monomers functionalized to form dicarboxylic acids or diesters. In one embodiment, copolymers with the following repeating formula (Formula III) are described. Within the context of the present invention, the repeating units of the copolymers in Formula III are not necessarily the same based on different (R¹, R², R³, R⁴ and R⁵) substituents in the repeating unit. In a preferred embodiment the repeating units of the copolymers in Formula III are the same.

R¹ and R² independently represent H or CH₃
R³ and R⁴ independently represent H or OCH₃
R⁵ independently represents C_1-16alkyl
R⁷ independently represents C_1-20alkyl; benzene or furan
n = 0-3
m = >10

Formula III

The copolymers of formula III are synthesized from the condensation between monomers in Formula VI and a dicarboxylic acid (or a mixture of dicarboxylic acids) or a diester (or a mixture of diesters) such as represented hereinbelow, according to the above-mentioned polymerization process. Therefore, also R⁷ can vary in the polymeric structure. It is also possible to transform the dicarboxylic acids into their esters prior to reaction by transesterification with an alcohol of up to four carbon atoms, but preferably methanol is used. Furthermore, additional diols or diacids can be added in order to tune the properties of the resulting polymer.

R¹ and R² independently represent H or CH₃
R³ and R⁴ independently represent H or OCH₃
R⁵ independently represents C_1-16alkyl
n = 0-4

Formula VI

R⁷ independently represents C_1-20alkyl; benzene or furan
R⁸ represents H or C_1-4alkyl

The aliphatic dicarboxylic acids comprising 2-20 carbon atoms include, but are not limited to, oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, muconic acid or a mixture of two or more herof; dimer fatty acids such as Pripol 1009 from Croda® or Radicarboxylic acid 0976 from Oleon®; and a mixture of two or more hereof. The aromatic dicarboxylic acids can be 2,5-furandicarboxylic acid, phtalic acid, isophtalic acid, terephtalic acid, any isomer of naphthalenedicarboxylic acid, or a mixture of two or more hereof. The above mentioned acids can all be bio-based. The esters of the above mentioned dicarboxylic acids might be used as well in the condensation.
Mixtures of dicarboxylic and tricarboxylic acids might be used. This might be required to expand the functionality when there are some monofunctional monomers present in the monomer mixture that would act as a chain end for the polymer. Tricarboxylic acids that might be used in combination with the above mentioned dicarboxylic acids include but are not limited to citric acid, isocitric acid, propane 1,2,3, tricarboxylic acid trimesic acid. Mixtures of dimer and trimer fatty acids such as Pripol 1006, Pripol 1025 and Pripol 1040 from Croda® might also be used. Polyacids such as tannic acid might also be used in combination with dicarboxylic acids. The esters of the above mentioned dicarboxylic acids might be used as well in the condensation reaction.
In another embodiment, copolymers with the following repeating formula (Formula IVa) are described. Within the context of the present invention, the repeating units of the copolymers in Formula IVa are not necessarily the same based on different (R¹, R², R³, R⁴, R⁵ and R⁷) substituents in the repeating units. In a preferred embodiment the repeating units of the homopolymers in Formula IVa are the same.

R¹ and R² independently represent H or CH₃
R³ and R⁴ independently represent H or OCH₃
R⁵ independently represents C_1-16alkyl or (C=O)C_2-3alkyl
R⁷ independently represents C_2-20alkyl, CH₂furanCH₂ or benzene
n = 0-2
m = >10

Formula IVa

The copolymers with formula IVa can be synthesized from the condensation between monomers in Formula VII and a diol or a mixture of diols, such as represented hereinbelow, according to the above mentioned polymerization process. Therefore, R⁷ can vary in the polymeric structure. Lignin-derived monomers might be dicarboxylic acids or diesters. The latter can be derived from the dicarboxylic acids by transesterification. Furthermore, additional diols or diacids can be added in order to tune the properties of the resulting polymer.

⁷

_2-20

The aliphatic diols comprising 2-20 carbon atoms include but are not limited to ethylene glycol, diethylene glycol, 1,3-propanediol, propane-1,2-diol, 1,4-butanediol, 1,6-hexanediol or or a mixture of two or more hereof; dimer diols such as Radianol 1990 from Oleon® or or a mixture of two or more hereof. The above mentioned diols can all be bio-based. The aromatic diols comprise, but are not limited to catechol, resorcinol hydroquinone and furan-2,5-diyl)dimethanol. Besides diols, polyols can be used. These include but are not limited to glycerol, trimethylolpropane, and pentaerythritol. Mixtures of diols and polyols can be used. This is especially interesting to expand the functionality when there are some monofunctional monomers present in the monomer mixtures that would act as a chain end.
In another embodiment, copolymers with the following repeating formula (Formula IVb) can be synthesized from the condensation between monomers in Formula VIII and a diol or a mixture of them according to the above mentioned polymerization reaction. Within the context of the present invention, the repeating units of the copolymers in Formula IVb are not necessarily the same based on different (R¹, R², R³, R⁴, R⁵ and R⁷) substituents in the repeating units. In a preferred embodiment the repeating units of the polymers in Formula IVb are the same.

Formula IVb

The copolymers with formula IVb are synthesized from the condensation between monomers in Formula VIII and a diol or a mixture of diols as represented hereinbelow, according to the above mentioned polymerization process. Therefore, R⁷ can vary in the polymeric structure. Lignin-derived monomers in formula VIII might be dicarboxylic acids or diesters. The latter can be derived from the dicarboxylic acids by transesterification. Furthermore, additional diols or diacids can be added in order to tune the properties of the resulting polymer.

⁷

₂₀

The polymerisation reactions described above can be summarized by Scheme I shown in Fig. 5.
The invention is also directed to the use of the polyesters according to the invention. The polyesters can be used in different applications, mainly as a replacement of semi-aromatic polyesters, of which PET is the best know example. Possible applications of the polyesters according to the invention are textile (apparel and house furnishing), bottle (water and other drinks, as well as other liquids such as detergents) and films for packaging. Moreover, the polyesters according to the invention can be used as a finish on wood products. Fibers from the polyesters according to the invention may be used for car tire reinforcements and as insulating and cushioning material. In these applications the polyesters according to the invention can replace existing polyesters.
It is further noted that the invention relates to all possible combinations of features described herein, preferred in particular are those combinations of features that are present in the claims.
It is further noted that the term 'comprising' does not exclude the presence of other elements. However, it is also to be understood that a description on a product comprising certain components also discloses a product consisting of these components. Similarly, it is also to be understood that a description on a process comprising certain steps also discloses a process consisting of these steps.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the invention will now be described in more detail with reference to the appended drawings, wherein same reference numerals illustrate same features.

Figure 1 represents 1H NMR spectrum of monomer 1.
Figure 2 represents 1H NMR spectrum of monomer 2.
Figure 3 represents 1H NMR spectrum of monomer 5.
Figure 4 represents IR spectrum of the conversion of acid groups to ester bonds in polyester according to example 9.
Figure 5 represents Scheme I summarizing the polymerisation reactions according to aspects of the invention.

DESCRIPTION OF EMBODIMENTS

The invention will now be explained by way of the following examples without however being limited thereto.

Synthesis of the monomers

Example 1: Transformation of phenolic hydroxyl group in aliphatic hydroxyl. Preparation of 3-(4-(2-hydroxyethoxy)-3-methoxyphenyl)propan-1-ol (monomer 1)

3 grams (1 equiv.) of dihydroconiferyl alcohol (4-(3-Hydroxypropyl)-2-methoxyphenol) was mixed with etylene carbonate (20 equiv.) and K₂CO₃ (2 equiv.). It was stirred at 120 °C for 20h. After cooling down it was quenched with 10 ml of water and 50ml of ethylacetate (EtOAc) and 50ml of brine were added. The organic phase was washed with ethyl acetate, and it was purified by column chromatography using 100% EtOAc. The product was isolated and characterized by 1H NMR (Figure 1).

Example 2: Preparation of 3-(4-(3-hydroxypropoxy)-3-methoxyphenyl)propan-1-ol. (Monomer 2)

3 grams (1 equiv.) of dihydroconiferyl alcohol (4-(3-Hydroxypropyl)-2-methoxyphenol) was mixed with 3-chloro-1 propanol (1.5 equiv.) and NaOH and refluxed in iso-propanol for 16h. After cooling down the iso-propanolwas evaporated and water and EtOAc were added. The organic phase was extracted with EtOAc and purified by column chromatography using 100% EtOAc. The product was isolated and characterized by 1H NMR (Figure 2).
Similar transformations of the phenolic hydroxyl group in aliphatic hydroxyl were possible in the manufacturing of the following monomers.

• Example 3: Preparation of 3-(4-(3-hydroxypropoxy)-3,5-dimethoxyphenyl)propan-1-ol. (monomer 3)
Wherein 3 grams (1 equiv.) of 3-(4-(3-hydroxypropoxy)-3,5-dimethoxyphenol was mixed with 3-chloro-1 propanol (1.5 eq.) and NaOH and refluxed in iso-propanol for 16h.
• Example 4. Preparation of a mixture of 3-(4-(3-hydroxypropoxy)-3-methoxyphenyl)propan-1-ol and 3-(4-(3-hydroxypropoxy)-3,5-dimethoxyphenyl)propan-1-ol (monomer 4).
Wherein (1 equiv.) of dihydroconiferyl alcohol (4-(3-Hydroxypropyl)-2-methoxyphenol) and (1 equiv.) of 3-(4-(3-hydroxypropoxy)-3,5-dimethoxyphenol was mixed with 3-chloro-1 propanol (3.0 equiv.) and NaOH and refluxed in iso-propanol for 16h.

Example 5: Transformation of phenolic hydroxyl group in carboxylic acid. Preparation of 2-(4-(3-hydroxypropyl)-2-methoxyphenoxy)acetic acid. (monomer 5)

3 grams (1 equiv.) of dihydroconiferyl alcohol (4-(3-Hydroxypropyl)-2-methoxyphenol) was mixed in water with NaOH (1.2 equiv.) and stirred for 30 min at 60°C. Sodium chloroacetate (1.2 equiv.) were added and stirred at 60°C 20h. The reaction was allowed to cool down and HCI (36%) was added until pH 1, and the mixture was stirred for 30 min. A white precipitate was formed, which was filtered, washed with H₂O and dissolved with 50 ml of EtOAc. The organic layer was dried with MgSO₄ and the solvent removed under vacuum. The residue was purified by recrystallization (dichloromethane). The product was isolated and characterized by 1H NMR (Figure 2).
Similar transformations of the phenolic hydroxyl group in carboxylic acid were possible in the manufacturing of the following monomers.

Example 6: Preparation of 4-(4-(3-hydroxypropyl)-2-methoxyphenoxy)-4-oxobutanoic acid. (monomer 6)

Further modifications of the phenolic and or aliphatic hydroxyl group in the monomers could be used to introduce further carboxylic acids into the building blocks of the polymers according to the invention.
Such further modifications include:

Example 7. Oxidation of monomer 3 to dicarboxylic acid (monomer 7)
Example 8: Transformation of both phenolic and aliphatic hydroxyl group in carboxylic (monomer 8)

Synthesis of the Polymers

Example 9: Co-polymerization of monomer 1 with sebacic acid. (Polymer 1)

0.5 g of monomer 1 was mixed at 150°C with 0.445 g of sebacic acid, and 1 mol% of titanium isopropoxide was added. It was stirred at 150°C for 16h, after which it was heated at 180°C for 3 h under vacuum. Full conversion to the polyester was determined by transformation of acid groups in sebacic acid to ester bonds (Figure 4). The resulting polymer had a T _g of -16°C.
Analogous Co-polymerization reactions are possible for:

Example 10: Co-polymerization of monomer 2 with sebacic/adipic acid.
Example 11: Co-polymerization of monomer 3 with sebacic/adipic acid.
Example 12: Co-polymerization of monomer 4 with sebacic/adipic acid.
Example 13: Co-polymerization of monomer 7 with ethylene glycol.
Example 14: Co-polymerization of monomer 8 with ethylene glycol.

Claims

A polyester comprising the following repeating unit of formula I:
wherein:
R¹ and R² independently represent H or CH₃,

R³ and R⁴ independently represent H or OCH₃,

R⁵ independently represents C_1-16alkyl-O(C=O)R⁷(C=O); C_1-16alkyl(C=O);

(C=O)C_2-3alkyl(C=O); C_1-16alkyl(C=O)OR⁷O(C=O)C_1-16alkyl;

C_1-16alkyl(C=O)OR⁷ or (C=O)C_2-3alkyl(C=O)OR⁷O(C=O)C_2-3alkyl,

R⁷ independently represents C_1-20alkyl; benzene or furan,

R⁶ represents CH₂ or (C=O),

n = 0-3,

m ≥ 10.
A polyester according to claim 1, comprising a repeating unit of formula II:

R¹ and R² independently represent H or CH₃

R³ and R⁴ independently represent H or OCH₃

R⁵ represents C_1-16alkyl or (C=O)C_2-3alkyl

n = 0-3

m = >10
A polyester according to claim 1, comprising a repeating unit of formula III:

R¹ and R² independently represent H or CH₃

R³ and R⁴ independently represent H or OCH₃

R⁵ independently represents C_1-16alkyl

R⁷ independently represents C_1-20alkyl; benzene or furan

n = 0-3

m = >10
A polyester according to claim 1, comprising a repeating unit of formula IV:

R¹ and R² independently represent H or CH₃

R³ and R⁴ independently represent H or OCH₃

R⁵ independently represents C_1-16alkyl(C=O)OR⁷O(C=O)C_1-16alkyl or C_1-16alkyl(C=O)OR⁷ or (C=O)C_2-3alkyl(C=O)OR⁷O(C=O)C_2-3alkyl

R⁷ independently represents C_1-20alkyl; benzene or furan

R⁶ represents CH₂ or (C=O)

n = 0-3

m = >10
A process for the preparation of the polyesters according to any one of the claims 1-4, wherein the monomer or monomer mixture is heated in the presence of a catalyst to a temperature of 100-300 °C under a pressure below 10 kPa .
The process according to claim 5 wherein the catalyst is chosen from a metal oxide such as Sb₂O₃, GeO₂, TiO₂, PbO or MgO; a metal alkoxide such as Ti(OC₄H₉)₄, Ti[OCH(CH₃)2]₄ or Zr(OC₄H₉)₄; a metal acetate such as Mg(OCOCH₃)₂, Mn(OCOCH₃)₂, Zn(OCOCH₃)₂, Sb(OCOCH₃)₃ or Sn[OCO(C₂H₅)CH(CH₂)CH₃]₂; a (Lewis) acid such as H₂SO₄, polyphosphoric acid or SnCI; or any combinations thereof.
The process according to claim 5 or 6, wherein the polyester is a homopolymer and is prepared by polymerizing lignin-based monomers according to formula V:

R¹ and R² independently represent H or CH₃

R³ and R⁴ independently represent H or OCH₃

R⁵ represents C_1-16alkyl or (C=O)C_2-3alkyl

R⁸ represents H or C_1-4alkyl

n = 0-3
The process according to claim 5 or 6, wherein the polyester is a copolymer and is prepared by copolymerizing lignin-based monomers according to formula VI:

R¹ and R² independently represent H or CH₃

R³ and R⁴ independently represent H or OCH₃

R⁵ independently represents C_1-16alkyl

n = 0-3
The process according to claim 8, wherein the comonomer is a diacid, a polyacid, or a mixture of or a mixture of two or more hereof; a diester, a polyester or or a mixture of two or more hereof.
The process according to claim 5 or 6, wherein the polyester is a copolymer and is prepared by copolymerizing lignin-based monomers according to formula VII:

R¹ and R² independently represent H or CH₃

R³ and R⁴ independently represent H or OCH₃

R⁵ independently represents C_1-16alkyl or (C=O)C_2-3alkyl

R⁶ represents H or C_1-4alkyl

n = 0-3
The process according to claim 5 or 6, wherein the polyester is a copolymer and is prepared by copolymerizing lignin-based monomers according to formula VIII:

R¹ and R² independently represent H or CH₃

R³ and R⁴ independently represent H or OCH₃

R⁵ independently represents C_1-16alkyl or (C=O)C_2-3alkyl

R⁶ independently represents H or C_1-4alkyl

n = 0-3
The process according to claim 10 or 11, wherein the comonomer is a diol, a polyol or a mixture of two or more thereof.
The process according to any one of claims 7, 8, 10 or 11, wherein the lignin-based monomers are derived by modification of lignin-based precursors with the structure according to formula A:

R¹ and R² independently represent H or CH₃

R³ and R⁴ independently represent H or OCH₃

R = CH₃ or OH

n = 0-4
Process according to claim 13, wherein the lignin-based monomers are obtained by modification of the phenolic hydroxy group and/or the modification of the aliphatic hydroxyl group of a lignin-based precursor according to formula A.
Use of the polymers according to any one of claims 1-10 in textile, bottles, and films for packaging.